The invention relates to a process for the electric welding of two weld parts by means of the flow of current via the welding point to produce a melt pool of metal for the weld and the use of fluid e.g. gas to prevent or eliminate, or at least inhibit, oxidation at the welding point and to a weld part for application of this process.
The welding of two parts using a particular fluid or gas to prevent or eliminate oxidation at the welding point, in particular a protective gas, is described in many publications. Reference is made, for example, to DE-PS 29 33 863 which relates to a device for the welding of a stud to a workpiece in which a drawn arc is produced and gas streams extend round the stud and are directed from the exterior onto the welding point by means of an external gas supply.
Protective gas has also already been used in resistance welding. According to EP Application 0 302 333, the protective gas is blown from the exterior onto the welding point.
With known welding processes, the welding point has been screened by bell-like covers in order to intensify the effect of a supplied gas, in particular a protective gas, introduced into the covers. The introduced gas can either issue through openings between the cover and the respective workpiece or can expel the air previously contained in the cover (see DE-PS 26 47 845 and DE-PS 31 49 835). However, it is also known from DE-OS 28 18 896 to place a cover of this type onto the surface of the respective workpiece in a sealing manner and to exhaust the air to be driven out, via a particular aspirator.
This method of supplying a particular gas, in particular protective gas, from the exterior results in considerable gas consumption; if a cover is not used, the gas also whirls air into the welding point and this has to be compensated by a correspondingly high supply of gas. If a cover is used, its interior first has to be flushed free of air and this also correspondingly increases the actual gas consumption intended for the welding point. Furthermore, this flushing process leads to a corresponding delay in the initiation of welding as it is necessary to wait until substantially all remnants of air in the cover are flushed out.
It is an object of the present invention is to provide a process of the kind mentioned above such that the effect of supplying a particular fluid, e.g. gas to the welding point is improved with respect to the time and to the fluid requirement.